Add warning to use dotnet pack instead of nuget pack

[mcm-ham]

It could be helpful to add a warning on this page that you need to use dotnet pack instead of nuget pack. If you do the later views within package do not work and took me awhile to figure out my mistake. Seems like confusion other developers experienced https://stackoverflow.com/q/52451475/222748

Because dotnet nuget pack didn't work and dotnet nuget --help gave no information pack existed I then downloaded the latest nuget.exe from https://docs.microsoft.com/en-us/nuget/install-nuget-client-tools.

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Document Details

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• ID: 9fd019c7-ceb7-6ef3-26ba-6b44341b6fc5
• Version Independent ID: fd116d00-0dc7-efaf-c714-34d77b345a05
• Content: Reusable Razor UI in class libraries with ASP.NET Core
• Content Source: aspnetcore/razor-pages/ui-class.md
• Product: aspnet-core
• Technology: aspnetcore-razorpages
• GitHub Login: @Rick-Anderson
• Microsoft Alias: riande

[Rick-Anderson]

You need to use dotnet pack instead of nuget pack.

@pranavkm should I add this to the article?

[zbecknell]

I was chasing my tail trying to find this solution. Thank you mcm-ham!

[Rick-Anderson]

Moved to Master issue: Create reusable UI using the RCL project #16639

[MackinnonBuck]

This was done in #16414